JPS5896562A - Ink supply device - Google Patents

Abstract

PURPOSE:To shut off variation in the ink pressure during acceleration and deceleration of the head scanning from its transmission to the head by providing a fluid control valve that has a movable element in a chamber with two openings. CONSTITUTION:In a chamber 3 that has two openings a sphere-shaped movable element with a diameter larger than the openings and smaller than the inner diameter of the control portion of the chamber 3 is installed to form a fluid control valve. This fluid control valve is installed near the head 1 of an ink supply tube 2 that is connected to an ink jet 1. With this arrangement, if, for instance, the head 1 that was moving to the left stops and it is accelerated again to the right, the inertia of the ink in the ink supply tube 2 that was moving to the left gives high pressure change component in the positive direction to a point A, but the movable element 4 moves to the left to close the opening on the left side or in the reversed case, the opening on the right side is closed. Accordingly pressure difference is not transmitted to the head 1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to an inkjet in which the head is scanned.
The purpose of this invention is to suppress fluctuations in ink pressure within an ink supply pipe connected to a head and obtain stable ink pressure.

In a device such as an inkjet head that ejects ink for recording, one of the important issues is to maintain the ink meniscus at the ink ejection port in a stable state. Especially in ink-on-demand type inkjet heads,
The state of the meniscus of the ink ejection port is one of the factors that determines the minimum drive voltage required for ink ejection. Furthermore, when the ink pressure fluctuations generated in the ink supply pipe connected to the head are propagated inside the head,
The state of the meniscus at the ink ejection port becomes extremely unstable, causing the following serious drawbacks.

That is, when the pressure fluctuation of the ink acts on the positive pressure side, the meniscus of the ink ejection port is pushed toward the recording paper side and flies as a droplet. This phenomenon is noticeable in heads with airflow effects. When the negative pressure is applied to the negative pressure side, the meniscus of the ink ejection port becomes concave toward the inside of the head and breaks, allowing air to enter the head in the form of bubbles. The resulting ink pressure waves are absorbed by air bubbles, resulting in unstable ink ejection and, in severe cases, inability to eject.The minimum value of the ink pressure fluctuation that causes the above negative effects is So, ±O* 05”I
This is a small value of F/cm.

The ink pressure fluctuations that make the meniscus of the ink ejection port unstable as described above are mostly caused by vibrations and impacts of the ink supply tube, so it is necessary to smooth the movement of the ink supply tube. However, this alone cannot sufficiently suppress ink pressure fluctuations. That is, when the ink supply tube undergoes accelerated movement, a relative movement occurs between the ink supply tube and the ink, resulting in pressure fluctuations that are propagated to the head. This will be explained in more detail with reference to FIG.

FIG. 1a shows a scanning system of a head and an ink supply tube. An ink supply tube 2 is connected to the head 1 in a U-shape on one side, and is indicated by a dotted line in the figure. and 111. The pressure fluctuation of the ink at point A at this time, that is, the pressure fluctuation propagated to the head 1 and the scanning speed of the head 1, are shown in FIG. 1, with time VC plotted on the horizontal axis. In Figure 1a, head 1 is i, ii, i
The state in position ii is shown in Figure 1 as i, respectively.
Corresponds to ii and iii. In state 11 of a, that is, when the head 1 is moving at a constant velocity, most of the time is A.
The pressure variation at the point is 0 (11 of b). However, a
If the head 1 starts to decelerate, stops, and then accelerates in the opposite direction again, the inertia of the ink in the ink supply tube (upper part of the horizontal U-shape) that was moving to the left causes A
A high pressure fluctuation on the positive pressure side occurs at the point (1 of b).

On the other hand, in state 111 of a, there is almost no fluctuation in the ink pressure inside the ink supply tube (upper part of the horizontal U-shape) that was moving to the right. is pulled, and the pressure fluctuation is as follows:
This occurs slightly on the negative pressure side (111 in b). Therefore, in the head scanning system as shown in FIG. 1, when the head comes to position 1, the pressure fluctuation at point A becomes the largest, and the state of the meniscus at the ink ejection port becomes unstable. FIG. 2 shows a head scanning system in which the ink pressure fluctuations are the same when the head reaches the left end 1 and the right end 111.

As shown in FIG. 2a, the ink supply tube 2 is provided oppositely to the one shown in FIG. By making the ink supply tube 2 into a loop shape, the ink inside the tube 2 moves, albeit slightly, within the loop in the states 1 and 111 where it is subjected to acceleration, so the pressure fluctuation at point A is as shown in Figure 1. Since it is smaller than 1 and is symmetrical, the same value is shown for the position 111.

The ink pressure fluctuation at point A near the head shown in FIGS. 1 and 2 increases with the scanning speed and acceleration of the head 1. When the scanning of the head 1 is sub-scanning as in the case of a cylindrical scanning method, the scanning speed is slow and almost no problem occurs. However, in the case of main scanning, such as in a plane scanning method, this problem becomes more important.

It is an object of the present invention to block and alleviate ink pressure fluctuations in the vicinity of the head, particularly during acceleration and deceleration of head scanning, so that the fluctuations do not propagate to the head.

The present invention is characterized in that a fluid control valve having a movable element is provided inside a chamber having two openings.

FIG. 3 shows an embodiment of the present invention. 3 is a tubular body whose inner diameter is largest at the center and smallest at both ends, and inside the body 3 is a steel ball whose diameter is smaller than the inner diameter of the center and larger than the inner diameter of both ends. There is a spherical movable element 4 like this. FIG. 4 shows the pressure fluctuation at point A and the scanning speed of the head when the head 1 is scanned in this apparatus. Now, in Figure 3, head 1
If scanning to the right is the speed of ■, then 1 in Figure 4,
That is, when acceleration is applied in the O direction, the spherical movable element 4 in FIG. 3 receives the force and moves to the left side of the body 3, blocking the opening on the left side to prevent pressure fluctuations from propagating.

On the other hand, as shown in FIG. 4 111, when acceleration (3) is applied, the opening on the right side of the body 3 is closed to prevent pressure fluctuations from propagating. In the state shown in FIG. 4 and 11, that is, when the head 1 is scanning at a constant speed, the spherical movable element 4 is located approximately at the center of the body 3 and does not block the ink supply pipe 2.

The most significant feature of this fluid control valve is that the movable element 4 blocks the ink supply pipe 2 during acceleration and deceleration when the pressure fluctuations propagated to the head 1 are the largest, making it difficult for pressure fluctuations to be propagated to the head 1. In reality, some pressure fluctuation is propagated toward the head 1 until the spherical movable element 4 closes the opening, but the amount is small as shown in FIG. 4. In order to more completely block pressure fluctuations, the movement stroke 2 of the spherical movable element 4 is made as short as possible, and the spherical movable element 4
It is necessary to make the difference between the diameter of the ink and the inner diameter of the central part of the body 3 as small as possible, but it must be determined with consideration to ensuring the minimum amount of ink supply.

Further, FIG. 6 shows an example in which the present invention is applied to the head scanning system shown in FIG. 2, and FIG. 6 shows the pressure fluctuation at that time. In this case, fluid control valves are installed in the ink supply pipes 2 near the head 1, which are branched from the head 1. The operation is the same as that shown in FIG. 3, and the explanation will be omitted. Since the head scanning system shown in FIGS. 3 and 4 is symmetrical, more stable ink pressure can be obtained.

As described above, the present invention is an ink supply device characterized in that a part of the ink supply pipe near the head is equipped with a fluid control valve having a movable element inside a chamber having two openings. It is possible to sufficiently block and alleviate ink pressure fluctuations that occur during acceleration and deceleration of head scanning.

[Brief explanation of drawings]

FIGS. 1a and 1b are a schematic diagram showing a scanning system of an ink supply device in a conventional inkjet head recording apparatus and its operating characteristics, and FIG. 2d is a diagram showing the scanning system of an ink supply device in a conventional inkjet head recording apparatus. b is a schematic diagram showing the scanning system of another conventional ink supply device and its operating characteristic diagram, FIG. 3 is a partially sectional side view of the ink supply device in an embodiment of the present invention, and FIG. FIG. 6 is a partial cross-sectional side view of another embodiment of the ink supply device according to the present invention, and FIG. 6 is an explanatory diagram of the operation of the inkjet recording device shown in FIG. be. 1..." Rad, 2-0... Ink supply pipe, 3.
・100. Body, 4 @@@@@@ Spherical movable element. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure (Q) (Figure 3, Figure 4, Figure 5, Figure 6)

Claims (3)

[Claims] (1) A valve having a movable element arranged inside a chamber having two openings and having a diameter larger than the diameter of the two openings and smaller than the inner diameter of the central part of the chamber is connected to the head near the inkjet head. An ink supply device characterized by being provided in a part of an ink supply pipe. (2) The ink viscosifying device according to claim 1, wherein the movable element is spherical. (3) A patent application characterized in that the ink supply pipe branches into two directions and a valve is arranged in each ink supply pipe section. The ink supply device according to claim 1.